Servlet之Request对象

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我是靠谱客的博主高挑狗，最近开发中收集的这篇文章主要介绍Servlet之Request对象，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

一 Request对象的继承体系结构

ServletRequest       --   接口
   |   继承
HttpServletRequest   -- 接口
   |   实现
org.apache.catalina.connector.RequestFacade 类(tomcat)

1. 当我们写一个Servlet类实现Servlet接口时

package cn.itcast.web.servlet;
import javax.jws.WebService;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/servlet01")
public class ServletDemo01 implements Servlet {
@Override
public void init(ServletConfig servletConfig) throws ServletException {
}
@Override
public ServletConfig getServletConfig() {
return null;
}
//提供服务的方法
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
System.out.println(servletRequest);
}
@Override
public String getServletInfo() {
return null;
}
@Override
public void destroy() {
}
}

注意service()方法中传递的参数类型是ServletRequest servletRequest。

当我们把这个对象打印出来时，发现Tomcat传递的实际参数类型是org.apache.catalina.connector.RequestFacade

2. 当我们写一个Servlet类继承GenericServlet类时

package cn.itcast.web.servlet;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/servlet02")
public class ServletDemo02 extends GenericServlet {
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
System.out.println(servletRequest);
}
}

注意service()方法中传递的参数类型是ServletRequest servletRequest。

当我们把这个对象打印出来时，发现Tomcat传递的实际参数类型是org.apache.catalina.connector.RequestFacade。

2. 当我们写一个Servlet类继承HttpServlet类时

package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servlet03")
public class ServletDemo03 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println(req);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("doPost方法...");
}
}

注意doGet()和doPost()方法中传递的参数类型是HttpServletRequest req。

当我们把这个对象打印出来时，发现Tomcat传递的实际参数类型是org.apache.catalina.connector.RequestFacade。

二通过Request对象获取请求数据消息

1. 获取请求行数据
   * GET /day14/demo1?name=zhangsan HTTP/1.1
   * 方法：
       1. 获取请求方式：GET
           * String getMethod()
       2. (*)获取虚拟目录：/day14
           * String getContextPath()
       3. 获取Servlet路径: /demo1
           * String getServletPath()
       4. 获取get方式请求参数：name=zhangsan
           * String getQueryString()
       5. (*)获取请求URI：/day14/demo1
           * String getRequestURI():       /day14/demo1
           * StringBuffer getRequestURL() :http://localhost/day14/demo1

           * URL:统一资源定位符： http://localhost/day14/demo1   中华人民共和国
           * URI：统一资源标识符 : /day14/demo1                   共和国

       6. 获取协议及版本：HTTP/1.1
           * String getProtocol()

7. 获取客户机的IP地址：
* String getRemoteAddr()

案例：输入的网址是http://localhost:8080/day13_Servlet/requestDemo01?name=zhangsan

package cn.itcast.web.request;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取请求行数据
*/
@WebServlet("/requestDemo01")
public class RequestDemo01 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1. 获取请求方式
String method = req.getMethod();
System.out.println(method);//结果：GET
//2. (*)获取虚拟目录：/day14
String contextPath = req.getContextPath();
System.out.println(contextPath);//结果：/day13_Servlet
//3. 获取Servlet路径: /demo1
String servletPath = req.getServletPath();
System.out.println(servletPath);//结果：/requestDemo01
//4. 获取get方式请求参数
String queryString = req.getQueryString();
System.out.println(queryString);//结果：name=zhangsan
//5. (*)获取请求URI：/day14/demo1
String requestURI = req.getRequestURI();
System.out.println(requestURI);//结果：/day13_Servlet/requestDemo01
StringBuffer requestURL = req.getRequestURL();
System.out.println(requestURL);//结果：http://localhost:8080/day13_Servlet/requestDemo01
//6. 获取协议及版本：HTTP/1.1
String protocol = req.getProtocol();
System.out.println(protocol);//结果：HTTP/1.1
//7. 获取客户机的IP地址
String remoteAddr = req.getRemoteAddr();
System.out.println(remoteAddr);//结果：0:0:0:0:0:0:0:1，返回的是IPV6的地址
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
}
}

2. 获取请求头数据
   * 方法：
       * (*)String getHeader(String name):通过请求头的名称获取请求头的值
       * Enumeration<String> getHeaderNames():获取所有的请求头名称

package cn.itcast.web.request;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;
/**
* 演示通过Request对象获取请求行数据
*/
@WebServlet("/requestDemo02")
public class RequestDemo02 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//通过请求头的名称获取请求头的值
String host = req.getHeader("Host");
System.out.println(host);//结果：localhost:8080
String userAgent = req.getHeader("User-Agent");
System.out.println(userAgent);//结果：Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36
String accept = req.getHeader("Accept");//结果：
System.out.println(accept);//结果：text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3
String acceptLanguage = req.getHeader("Accept-Language");
System.out.println(acceptLanguage);//结果：zh-CN,zh;q=0.9
String acceptEncoding = req.getHeader("Accept-Encoding");
System.out.println(acceptEncoding);//结果：gzip, deflate, br
String referer = req.getHeader("Referer");
System.out.println(referer);//结果：null
String connection = req.getHeader("Connection");
System.out.println(connection);//结果：keep-alive
//获取所有的请求头名称
Enumeration<String> headerNames = req.getHeaderNames();
while (headerNames.hasMoreElements()) {
String headName = headerNames.nextElement();
System.out.print(headName + ":");
System.out.println(req.getHeader(headName));
}
/**
结果：
host:localhost:8080
connection:keep-alive
upgrade-insecure-requests:1
user-agent:Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36
accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,;q=0.8,application/signed-exchange;v=b3
sec-fetch-site:none
sec-fetch-mode:navigate
accept-encoding:gzip, deflate, br
accept-language:zh-CN,zh;q=0.9
cookie:JSESSIONID=CE853D0024D1E02C250D84171184B315; Idea-57b4784d=a9f88c09-1eab-4772-b057-6159cc7b8abf
**/
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
}
}

3. 获取请求体数据
   * 请求体：只有POST请求方式，才有请求体，在请求体中封装了POST请求的请求参数
   * 步骤：
       1. 获取流对象
           * BufferedReader getReader()：获取字符输入流，只能操作字符数据
           * ServletInputStream getInputStream()：获取字节输入流，可以操作所有类型数据
               * 在文件上传知识点后讲解
       2. 再从流对象中拿数据

package cn.itcast.web.request;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.util.Arrays;
import java.util.Enumeration;
/**
* 演示通过Request对象获取请求行数据
*/
@WebServlet("/requestDemo03")
public class RequestDemo03 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//通过getReader方式获取请求体
BufferedReader reader = req.getReader();
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);//结果：username=gao&password=123
}
}
}

4. 获取请求参数通用方式

不论get还是post请求方式都可以使用下列方法来获取请求参数
   1. String getParameter(String name):根据参数名称获取参数值 username=zs&password=123
   2. String[] getParameterValues(String name):根据参数名称获取参数值的数组 hobby=xx&hobby=game
   3. Enumeration<String> getParameterNames():获取所有请求的参数名称
   4. Map<String,String[]> getParameterMap():获取所有参数的map集合

   * 中文乱码问题：
       * get方式：tomcat 8 已经将get方式乱码问题解决了
       * post方式：会乱码
           * 解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8");

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>注册</title>
</head>
<body>
<form action="/day13_Servlet/requestDemo04" method="post">
<input type="text" placeholder="请输入用户名..." name="username"><br/>
<input type="text" placeholder="请输入密码..." name="password"><br/>
爱好：&nbsp
游泳<input type="checkbox" name="hobby" value="swimming">
跑步<input type="checkbox" name="hobby" value="running"><br/>
<input type="submit" value="注册">
</form>
</body>
</html>

package cn.itcast.web.request;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Map;
/**
* 演示通过Request对象获取请求体数据
*/
@WebServlet("/requestDemo04")
public class RequestDemo04 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
String username = req.getParameter("username");
System.out.println(username);
String password = req.getParameter("password");
System.out.println(password);
String[] hobby = req.getParameterValues("hobby");
System.out.println(Arrays.toString(hobby));
Enumeration<String> parameterNames = req.getParameterNames();
while(parameterNames.hasMoreElements()){
System.out.println(parameterNames.nextElement());
}
while(parameterNames.hasMoreElements()){
System.out.println(parameterNames.nextElement());
}
Map<String, String[]> parameterMap = req.getParameterMap();
for(Map.Entry<String,String[]> entry:parameterMap.entrySet()){
System.out.println(entry.getKey());
System.out.println(Arrays.toString(entry.getValue()));
}
}
}

5. 请求转发：一种在服务器内部的资源跳转方式
   1. 步骤：
       1. 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
       2. 使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response)

   2. 特点：
       1. 浏览器地址栏路径不发生变化
       2. 只能转发到当前服务器内部资源中
       3. 即使转发，也只有一次请求，多个资源之间使用的是同一个请求

package cn.itcast.web.request;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取请求体数据
*/
@WebServlet("/requestDemo06")
public class RequestDemo06 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("requestDemo06被访问了");
// 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
RequestDispatcher requestDispatcher = req.getRequestDispatcher("requestDemo07");
//使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response) 
requestDispatcher.forward(req,resp);
}
}

package cn.itcast.web.request;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取请求体数据
*/
@WebServlet("/requestDemo07")
public class RequestDemo07 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("requestDemo07被访问了");
}
}

结果是：requestDemo06和requestDemo07都被访问了。

6. Request共享数据
   * 域对象：一个有作用范围的对象，可以在作用范围内共享数据
   * request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据
   * 共享数据的方法：
       1. void setAttribute(String name,Object obj):存储数据
       2. Object getAttitude(String name):通过键获取值
       3. void removeAttribute(String name):通过键移除键值对

package cn.itcast.web.request;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取请求体数据
*/
@WebServlet("/requestDemo06")
public class RequestDemo06 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("requestDemo06被访问了");
//给request对象存储数据
req.setAttribute("name","zhangsan");
// 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
RequestDispatcher requestDispatcher = req.getRequestDispatcher("requestDemo07");
//使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response) 
requestDispatcher.forward(req,resp);
}
}

package cn.itcast.web.request;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取请求体数据
*/
@WebServlet("/requestDemo07")
public class RequestDemo07 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("requestDemo07被访问了");
//通过request获取属性值
System.out.println(req.getAttribute("name"));//结果："zhangsan"
}
}

7. 获取ServletContext
* ServletContext getServletContext()

package cn.itcast.web.request;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 演示通过Request对象获取servletContext
*/
@WebServlet("/requestDemo08")
public class RequestDemo08 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext servletContext = req.getServletContext();
System.out.println(servletContext);
}
}